U.S. Customs and Border Protection selected four construction companies Thursday to erect prototypes of the Mexican border wall that President Donald Trump has said he intends to build to deter illegal immigration and smuggling.

The four firms, from four different U.S. states, are to build solid-concrete prototypes of the border wall within 30 days, once they are given a notice to proceed. Those four sample walls will then be tested for strength and “permeability,” according to the agency’s acting deputy commissioner, Ronald Vitiello.

The border protection agency is separately screening applicants for other contracts to build prototype walls made from alternate materials.

Trump has said he thinks the 10-meter-tall wall should have windows, or even be fully transparent, so Border Patrol officers in the United States can observe suspicious activities on the other side of the barrier.

“We’re going to use all the things that we think will work the best,” Vitiello said.

Thursday’s announcement was the latest step forward in a bureaucratic process that has been delayed multiple times. The administration once said construction of the full border wall would begin in June, but it was not until mid-March that the first requests for proposals went out to contractors, seeking conceptual designs for the border barrier, which has been shrouded in political controversy.

Congress has appropriated $20 million to CBP for use in preparing the prototypes, both of concrete and other materials. No funds have yet been budgeted for the full border wall, likely a multibillion-dollar undertaking that would be one of the largest public works projects in U.S. history.

The four companies selected Thursday to build concrete prototypes were Caddell Construction of Montgomery, Alabama; Fisher Industries of Tempe, Arizona; Texas Sterling Construction of Houston; and W.G. Yates & Sons of Philadelphia.
…